Injection device with torsion spring and rotatable display

ABSTRACT

The present invention relates to an injection device comprising a torsion spring operatively connected to a dose setting member being adapted to set a dose to be ejected from the injection device. A rotatably mounted display member adapted to display the dose to be ejected in accordance with a setting of the dose setting member is also provided. The rotatably mounted display member is adapted to be rotated over an angle corresponding to at least one revolution of the display member. The display member may be implemented as a dose indicator barrel having numerals arranged along a helical path on an outer surface thereof, or alternatively, as a counting device having two or more display wheels having numerals arranged on an outer surface thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/606,147, filed May 26, 2017, (Notice of Allowance mailed), which is acontinuation of U.S. application Ser. No. 14/167,558, filed Jan. 29,2014 (U.S. Pat. No. 9,687,611), which is a continuation of U.S.application Ser. No. 13/626,541, filed Sep. 25, 2012 (U.S. Pat. No.8,684,969), which is a continuation of U.S. application Ser. No.11/665,571, filed Dec. 5, 2007 (U.S. Pat. No. 8,357,120), which is a 35U.S.C. § 371 national stage application of International PatentApplication PCT/EP2005/011287 (published as WO 2006/045528), filed Oct.20, 2005, which claims priority of European Patent Application04077899.5, filed Oct. 21, 2004; this application further claimspriority under 35 U.S.C. § 119 of U.S. Provisional Application60/626,271, filed Nov. 9, 2004, all of which are hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to an injection device, such as a wind-uppen, wherein numerals indicating the dose to be ejected from theinjection device are displayed over an angle of rotation exceeding onerevolution. In particular, the numerals indicating the dose to beejected are arranged along a helical path, or alternatively, numeralsindicating the dose to be ejected are displayed on a counting device.The present invention ensures that an increased accuracy in dose settingmay be obtained.

BACKGROUND OF THE INVENTION

Various types of automatic injection devices have been described in theliterature. A majority of these automatic injection devices apply doseindicator barrels, dose indicator wheels or the like which, during dosesetting, are only allowed to rotate less than one single revolution. Thefact that the dose indicator barrel is only allowed to rotate less thanone revolution during dose setting puts a limit to the obtainableangular resolution. This limited angular resolution also limits theaccuracy of the dose setting procedure.

In prior art injection devices the dose setting scale arranged on theouter surface of the barrels or wheels contains only up to 42 scaleunits with an incremental of 2. Thus, the accuracy when setting a doseis limited by this rather rough incremental.

Examples of “one revolution” barrels or wheel may for example be foundin U.S. Pat. No. 5,725,508, EP 0 338 806 or U.S. Pat. No. 5,104,380.

WO 02/053214 discloses an automatic injection device having a doseindicator barrel capable of rotating more than one revolution. However,the injection device according to WO 02/053214 applies a linear springto move a piston rod in the distal direction of the injection device.Evidently, an injection device applying a linear spring has a built-inaxial displacement due to compressions and extensions of the linearspring along the axial direction of the injection device. This linearmovement may easily be utilized to provide axial movements of the doseindicator barrel. However, it is a disadvantage that linear springs arehighly non-linear in terms of force vs. compression. In addition, alinear spring exhibits relative high mechanical looses. Thus, due to theproblems relating to the non-linear properties and relatively highlooses there is a need for injection devices having linear and moreefficient injection assisting systems.

The above-mentioned problems may be solved by applying a torsion springinstead of the linear spring. An injection device applying a torsionspring is conceptually different from linear spring-based devices inthat torsion-based systems do not have a built-in axial movement of thespring assisting the user in injecting a dose of medicament from theinjection device. The advantages of torsion-based injection devices aremany, the greatest of these probably being that torsion springs respondin a linear manner over a large working range.

Thus, there is a need for a torsion spring-based injection deviceproviding an improved and more user friendly dose setting procedure. Itis an object of the present invention to provide such torsionspring-based injection device having an expanded dose scale with a highresolution.

SUMMARY OF THE INVENTION

The above-mentioned object is complied with by providing, in a firstaspect, an injection device comprising

-   -   a torsion spring operatively connected to a dose setting member,        the dose setting member being adapted to set a dose to be        ejected from the injection device, and    -   a rotatably mounted display member adapted to display the dose        to be ejected from the injection device in accordance with a        setting of the dose setting member, the rotatably mounted        display member being rotatable over an angle corresponding to at        least one revolution of the display member.

The display member may be adapted to be moved between two end positions.These two end positions may define or set an axial operation range ofthe display member. The axial operation range of the display member maybe associated with a substantially linear working range of the torsionspring. The working range of the torsion spring utilized to move thedisplay member between the two end positions may constitute only afraction of the available working range provided by the torsion spring.Thus, by applying a torsion spring only a small and linear working rangeof the available working range is utilized.

The display member may comprise a dose indicator barrel having numeralsarranged along a helical path on an outer surface thereof.

According to a first embodiment of the present invention, the injectiondevice may further comprise

-   -   a housing,    -   a piston rod having a threaded outer surface with a drive track        arranged in a longitudinal direction of the outer surface of the        piston rod,

wherein the dose setting member is rotatably mounted and defines apassage for the piston rod, the dose setting member further having aguiding track arranged on an inner surface thereof,

-   -   a rotatable drive member being adapted to at least partly engage        with at least part of the drive track of the piston rod so as to        drive the piston rod,

wherein the dose indicator barrel has a part engaging at least part ofthe guiding track of the dose setting member, the dose setting memberand the dose indicator barrel being movable in relation to each other,the dose indicator barrel further having a threaded outer surfacecooperating with a threaded inner portion of the housing whereby thedose indicator barrel undergoes a combined translational and rotationalmovement in relation to the housing upon rotation of the dose settingmember, and

wherein the injection device has a threaded portion cooperating with thethreaded outer surface of the piston rod so that rotation of the pistonrod relative to the housing results in a longitudinal movement of thepiston rod.

It is to be understood that the drive track dose not necessarily extendover the full length of the piston rod. For example, the drive track mayin some cases only extend over a part of the full length of the pistonrod. Also, the drive track arranged in the piston rod may be anindentation or groove in the longitudinal direction of the piston rod.Alternatively, it may also be a planar surface or two opposing planarsurfaces.

Similarly, it is to be understood that other arrangements in terms ofthe positioning of the threaded portion of for example the doseindicator barrel may be arranged differently.

According to a second embodiment of the present invention, the injectiondevice further comprises

-   -   a housing,    -   a piston rod having a threaded outer surface with a track        arranged in a longitudinal direction of the outer surface of the        piston rod,

wherein the dose setting member is rotatably mounted and defines apassage for the piston rod, the dose setting member further having aguiding track arranged on an inner surface thereof,

-   -   a rotatable drive member having a threaded portion cooperating        with at least part of the threaded outer surface of the piston        rod,

wherein the dose indicator barrel has a part engaging at least part ofthe guiding track of the dose setting member, the dose setting memberand the dose indicator barrel being movable in relation to each other,the dose indicator barrel further having a threaded outer surfacecooperating with a threaded inner portion of the housing whereby thedose indicator barrel undergoes a combined translational and rotationalmovement in relation to the housing upon rotation of the dose settingmember, and

wherein the injection device has a portion at least partly engaging thetrack of piston rod so that rotation of the drive member relative to thehousing results in a longitudinal movement of the piston rod.

The drive member may be adapted to be connected to the dose settingmember via a ratchet. This ratchet allows the dose setting member to berotated in both directions so that a given dose may be either increasedor reduced. Due to the force provided by the torsion spring onto theratchet, the dose setting member will remain in any position—i.e. dosevalue—to which it has been brought.

The dose setting member may be adapted to be separated from the drivingmember. This separation may be achieved in several ways. In one way theseparation may be obtained by a retraction of the dose setting member inthe axial direction of the injection device. The retraction of the dosesetting member must be over a distance sufficient to detach the dosesetting member or the drive member from the teeth of the ratchet. Otherseparation mechanisms, such as pushing the dose setting member ortwisting the dose setting member are also applicable.

The torsion spring may be arranged between the housing and the dosesetting member in such a way that when the dose setting member isrotated around the piston rod, the torsion spring is strained. Thetorsion spring may be a helical spring which extends coaxially with thepiston rod, and which interconnects the housing and the dose settingmember in such a way that rotation of the dose setting member, in orderto set the dose, strains the torsion spring.

The injection device may further comprise a locking member adapted tofixate the piston rod in such a way that no relative rotation of thepiston rod and the housing is possible when the locking member is in itslocking position. This fixation may be provided by a direct engagementof the locking member into the track of the piston rod, or via the drivemember. The injection device may further comprise a release buttonadapted to release the locking member from its locking position.Preferably, the release button is positioned in the distal half of thelength of the injection device.

The injection device may further comprise a first stopping member fordefining an outer position of the dose indicator barrel. This outerposition of the dose indicator barrel may correspond to a maximumobtainable dose. Another outer position of the dose indicator barrel,given by a second stopping member, may define a stop for providingfurther doses. The stopping members may form integral parts of the innersurface of the housing.

In a third embodiment, the display member may comprise a counting devicehaving two or more display wheels having numerals arranged on an outersurface thereof. In this second embodiment the counting device may havea first and a second wheel. When the dose setting member is rotated, thefirst wheel is rotated via an optional gear mechanism, such as a planetgear. This first wheel may contain numerals with an incremental of one.The total scale on this wheel may be from 0 to 9. The second wheel nextto the first wheel also contains numerals with an incremental of 1.However, this second wheel “counts” the number of revolutions of thefirst wheel, or alternatively, it “counts” the tens of the first wheelwith an incremental of one.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in further details withreference to the accompanying figures, wherein

FIG. 1 shows a cross-sectional view of a first embodiment of theinjection device according to the present invention,

FIG. 2 shows a cross-sectional view (rotated 90 degrees compared toFIG. 1) of a first embodiment of the injection device according to thepresent invention,

FIG. 3 shows a detailed cross-sectional view of a first embodiment ofthe present invention,

FIG. 4 shows a detailed cross-sectional view of a second embodiment ofthe present invention, and

FIG. 5 shows a detailed cross-sectional view of a third embodiment ofthe present invention.

FIG. 6 shows a cross-section of a key in a housing component.

FIG. 7 shows a cross-section view of a piston rod with a track.

While the invention is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and will be described in detail herein. Itshould be understood, however, that the invention is not intended to belimited to the particular forms disclosed. Rather, the invention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

In its most general aspect the present invention relates to an injectiondevice comprising a torsion spring in combination with a rotatable doseindicator mechanism capable of being rotated at least onerevolution—i.e. over an angle larger than 360 degrees. For example, thedose indicator mechanism may be implemented as a barrel (see FIGS. 1-4)or as interconnected wheels (see FIG. 5), the latter being operated as acounting device. In order to increase the angular resolution compared toknown dose indicator mechanisms the dose indicator mechanism of thepresent invention is rotatable over an angle of rotation correspondingto at least one revolution. The fact that the dose to be ejected isdisplayed over at least one revolution allows that the dose settingscale may contain at least 50, 60, 70, 80, 90, 100 units with anincremental of one.

FIGS. 1-3 show a cross-sectional view of the injection device accordingto a first embodiment of the present invention. The dose of medicamentto be ejected from the injection device is set by rotating dose settingmember 1. The dose setting member 1 is attached to the housing 5 of theinjection device via torsion spring 12. When the dose setting member 1is rotated in order to set a dose to be ejected from the injectiondevice, energy is accumulated in torsion spring 12. This energy may bereleased by releasing locking member 4 whereby the piston rod 2 willrotate and move in the distal direction of the injection device. Thedistal movement of the piston rod 2 is caused by a rotational movementof the piston rod 2 itself in that the piston rod 2 has a threaded outersurface. The threads of the piston rod 2 engage and co-operate with athreaded portion 3 of the injection device causing the piston rod 2 toperform the distal and axial movement.

The inner surface of housing 5 of the injection device is provided withthreads 10. These threads are adapted to engage and co-operate withouter threads 8 of a dose indicator barrel 9. The dose indicator barrel9 engages with sliding track 11 of the dose setting member 1 in such away that the dose indicator barrel 9 is able to slide in said slidingtrack 11 in an axial direction of the injection device.

When the dose setting member 1 is rotated in order to set a dose, thedose indicator barrel 9 rotates with the dose setting member 1 causingthe dose indicator barrel 9 to be axially displaced relative to thehousing 5. A window is provided in the housing 5 of the injectiondevice. Through this window, the user of the injection device may viewthe actual dose setting level from numerals (not shown) provided on anexterior surface of the dose indicator barrel 9. The numerals arearranged along a helical path.

An advantage of having the numerals arranged along a helical-like pathis that a higher angular resolution is obtainable when a dose is to beset. Due to this higher angular resolution a dose can be set with asignificantly higher accuracy. This greater accuracy is obtained sincethe helical-like path allows for more numerals to be arranged on thedose indicator barrel 9 compared to numerals arranged at the same heighton the surface of the dose indicator barrel 9.

When a dose has been ejected from the injection device, the doseindicator barrel 9 is adapted to be rotated back to its initial positionand it is thereby ready to be set to a new dose. The same applies for aninjection device applying a counting device as a dose meter.

As already mentioned, the piston rod 2 has a threaded outer surface.This threaded outer surface engages and co-operates with a threadedportion 3 of the injection device. The piston rod 2 is driven by thedrive member 6 that engages a track in piston rod 2. The axial movementof the piston rod 2 is provided by rotating piston rod 2 in the threadedportion 3 of the injection device. Drive member 6 may be locked by thelocking member 4. In its locked position, drive member 6 is preventedfrom rotating. In order to release the drive member 6, the user of theinjection device may activate a spring-loaded push button 15 wherebydrive member 6 causes the piston rod 2 to rotate in threaded part 3 ofthe housing whereby the piston rod 2 rotates and travels in the distaldirection of the injection device. Thus, when the drive member 6 isreleased, the injection device ejects automatically. During ejection,the dose indicator barrel returns to zero dose.

The dose setting member 1 and the drive member 6 are mechanicallyconnected via a self-tightening ratchet 13. Preferably, theself-tightening ratchet 13 has saw-toothed teeth with approximatelyvertical oriented flanks as the self-tightening flanks.

In order to reset or reduce an already set dose, the dose setting member1 is arranged to be axially retractable over a distance corresponding tothe height of the teeth of the one-way ratchet 13. Thus, by pulling thedose setting member 1 back, and thereby disengage the dose settingmember 1 from the drive member 6, an already set dose can be reduced oreven reset. The amount of reduction obviously depends on the angle ofrotation (in the opposite rotation direction as when a dose is set) ofthe dose setting member 1.

The self-tightening ratchet may be formed as a separate component havingfirst and second engaging parts. Alternatively, one of these parts mayform an integral part of the dose setting member 1, or alternatively, anintegral part the drive member 6.

FIG. 4 shows a second embodiment of the present invention. Compared tothe first embodiment, the drive member 6 has a threaded portioncooperating with the threaded outer surface of the piston rod 2. Themain difference compared to the first embodiment is that the piston rod2 is no longer rotatable relative to the housing 5. This non-rotatablerelationship is ensured in that the housing of the injection device hasa key 14 which at least partly engages the track 7 of piston rod 2.Thus, when the drive member 6 is free to rotate relative to the housing5 the piston rod 2 will undergo a translational movement along the axialdirection of the injection device.

FIG. 5 shows a third embodiment of the present invention. In thisembodiment the dose indicator barrel of the first and second embodimenthas been replaced by a counting device having two wheels 15, 16. Inprinciple the number of wheels may be chosen arbitrary, but forsimplicity, a counting device having only two wheels is illustrated inFIG. 5. The counting device is operated as follows: When the dosesetting member 1 is rotated, the wheel closest to the dose settingmember 15 is rotated via an optional planet gear 17. This wheel containsnumerals with an incremental of one. The total scale on this wheel maycontain 10 units distributed over a scale from 0 to 9, or alternatively,the total scale may contain for example 20 units distributed over twoscales each having a scale from 0 to 9.

The second wheel 16 next to the first wheel 15 also contains numeralswith an incremental of 1. However, this second wheel “counts” the numberof revolutions of the first wheel, or alternatively, it “counts” thetens of the first wheel with an incremental of one. Alternatively, thesecond wheel “counts” the number of half resolutions of the first wheelin case the first wheel contains a scale having 20 units.

1. An injection pen comprising: a housing; a dose setting member forsetting a dose, the dose setting member mounted to the housing so thatit may rotate relative to the housing, the dose setting member beingcapable of rotating in two directions, one direction to increase thesize of a dose and another direction to decrease the size of the dose; adose indicator barrel, wherein the dose indicator barrel comprises acounting device having at least one display wheel having numeralsarranged on an outer surface thereof, wherein the at least one displaywheel rotates when the dose setting member is rotated; a piston rodhaving a threaded outer surface with a track arranged in a longitudinaldirection of its outer surface, a rotatable drive member that engageswith the track or with the threaded outer surface of the piston rod todrive the piston rod, a torsion spring that stores energy when a userrotates the dose setting member to set a dose, the torsion springsupplying the energy to drive a dose of medication from the injectionpen; and a release button; wherein when the release button is activatedby the user, the release button causes the torsion spring to drive theset dose from the injection pen and the dose indicator barrel rotatesduring injection back to a zero position.
 2. An injection devicecomprising: a housing (5) with an inner surface provided with threads(10), a dose setting member (1) adapted to set a dose to be ejected fromthe injection device, a piston rod (2) having a threaded outer surfacewith a track (7) arranged in a longitudinal direction of its outersurface, a rotatable drive member (6) that engages with the track (7) orwith the threaded outer surface of the piston rod to drive the pistonrod (2), a torsion spring (12) for accumulating energy that isreleasable to rotate the drive member (6) whereby causing the piston rod(6) to move in a distal direction of the injection device to eject theset dose automatically, wherein, a rotatably mounted display member isoperatively connected with the dose setting member (1) such that whenthe dose setting member (1) is rotated in order to set a dose, thedisplay member rotates with the dose setting member (1) causing thedisplay member to be axially displaced relative to the housing (5) andis adapted to display the dose to be ejected from the injection devicein accordance with a setting of the dose setting member (1), a releasebutton positioned in a distal half of the length of the injection pen,wherein when the release button is activated by the user, the releasebutton causes the torsion spring to drive the set dose from theinjection pen and the dose indicator barrel rotates during injectionback to a zero position. the rotatably mounted display member isrotatable over an angle corresponding to at least one revolution, andthe display member further returns to return to zero during ejection.